DD is 4 (this week!). I only do one friend at a time. That's stressful enough because DS is almost 2 and wants to join in and tends to just barge in on their games.
He can't be unsupervised, obviously, and will INSIST on following the girls upstairs and they get very irate with him. He gets upset, I have to keep fetching him downstairs and almost always end up putting a dvd on for him to avoid WWIII lol!
BUT, I do them, sporadically, because it's one of DD's favourite things, and tbh, all the little friends she's had over so far have been very nice, calm and polite and it's very sweet to see how they play together and make each other giggle at that age.
I just tend to take the plunge and get the playdo out and push down my anal desire for them not to mix the colours .
I don't worry about floor as it's floorboards and I just tell myself I'll do one big sweep up when it's all over.
If there was a child that was badly behaved, genuinely, then I'm afraid I just wouldn't invite them back. Life's too short.
Re the dog issue, I'm afraid I can't blame the child. It's not her fault if she's afraid - you don't know the whys or wherefores of her reaction. My DD would have been fine around a dog until last week...when a dog attacked her whilst she was feeding the dogs and bit at her hand to get the bread she was throwing .